A prospective study of the renal abnormalities on excretion urography in 189 patients with homozygous sickle cell disease is presented. Demonstrable abnormalities were present in 69 percent but there was no correlation with symptomatology. Calyceal clubbing was the most common abnormality occurring in 39 percent of cases and its incidence increased with age. An unexpected high prevalence (23 percent) of papillary necrosis occurred and both sinuses and cavities were demonstrated. The reasons for this high prevalence are discussed. The urographic findings did not correlate significantly with hematological features of the disease. (AU)